PhD Student University of Utah Salt Lake City, Utah
Natural selection can promote repeatable outcomes in evolution, contributing to the idea of evolutionary determinism in different biological systems. Obligatory ant-plant symbiotic interactions have evolved multiple times and involve a wide array of both ant and plant partners. The subfamily Formicinae comprises a major clade of ants, with around 3000 species globally distributed. Among that clade, several genera are dominant components in most terrestrial ecosystems. Also, within that subfamily, there are instances of arboreal lineages engaged in unique symbiotic associations with understory plants. Those lineages are distributed throughout different biogeographical boundaries, with plant-ants found pantropically. By taking advantage of an available dataset of enriched ultraconserved elements (UCEs), we applied phylogenomic analyses to understand the tempo and mode of the evolution of ant-plant mutualisms within Formicinae. Mapping of the mutualistic lineages revealed that formicine genera involved in highly symbiotic relationships with plants evolved at least three times independently in the rainforests from the African, Indomalayan, and Neotropical regions. Moreover, those distant-related lineages share an impressive phenotypic similarity, with their natural histories extensively overlapping. Interestingly, our diversification analyses using BAMM showed that the evolution of ant-plant symbioses does not correspond to quick shifts in diversification rates for those formicine lineages. Finally, our divergence timing analyses estimated the age of those independent evolutions of obligatory associations to be young (between 2-15 Ma) and highly concurrent. Taking it all together, we suggest that obligatory ant-plant symbiotic interactions in a major clade of ants are remarkable and relatively recent cases of extreme convergent evolution.
